The present invention relates generally to an optical system, a finder optical system, a relay type finder optical system, an eyepiece optical system and a single-lens reflex camera, and more specifically to an optical system having a camera-shake correction function capable of preventing image-shakes by camera-shake (e.g., upon hand-hold photographing), a relay optical system designed especially for taking systems such as digital cameras, film cameras and video cameras, an eyepiece optical system having a wide field of view, a long eye relief and a compact total length, a compact relay type finder optical system using the same, and a single-lens reflex camera using the same.
Prior art finder optical systems having a camera-shake correction function include the following.
The finder optical system set forth in patent publication 1 is configured as shown in FIG. 45. In this optical system, the camera-shake correction lens L is located in a non-TTL finder optical system wherein the taking optical system is separate from the finder optical system. Then, the camera-shake correction lens L is decentered parallel with the optical axis of the finder optical system by means of a driving system A, thereby implementing correction of shakes of light incident from a subject on the optical system.
The optical system set forth in patent publication 2 is configured as depicted in FIGS. 46, 47 and 48. In FIGS. 46 and 47, the lens L that forms a part of the objective lens is moved vertically to the optical axis, and in FIG. 48, the eyepiece lens E is moved vertically to the optical axis. In this way, correction of camera-shake is implemented.
With the above prior arts, a lens group having a camera-shake preventive function, i.e., an anti-shake group is used. As this anti-shake group is decentered, it produces aberrations that lead to image-formation capability deteriorations. It also produces decentration distortion that may otherwise cause an image shape to turn asymmetric with respect to the optical axis. There is thus the need of preventing such image-formation capability deteriorations and asymmetric image shape due to anti-shake
Further, as the anti-shake group is heavy, it gives an increasing load to an actuator for the movement of the anti-shake group; that is, it is necessary to lighten the anti-shake group.
Furthermore, a low sensitivity to anti-shake causes an increase in the amount of movement of the anti-shake group. A high sensitivity to anti-shake, in contrast, renders control of movement of the anti-shake group difficult. To eliminate this problem, the sensitivity to anti-shake must be set at a proper value.
With anti-shake optical systems, much care must thus be taken of anti-shake functions.
The optical systems disclosed in patent publications 1 and 2 teach nothing about how the problems to be solved with anti-shake optical systems are addressed. In other words, these prior arts are still less than satisfactory in terms of practically optimum anti-shake methods, and how they are feasible. In particular, some patent publications do not present any optical path diagrams.
The optical systems disclosed in patent publications 1 and 2 are all directed to a non-TTL finder optical system with a taking optical system separate from a finder optical system.
By the way, single-lens reflex cameras comprising an image pickup plane smaller than conventional Leica-format size have been proposed and commercialized. Especially the market for single-lens reflex cameras using CCDs, C-MOSs or other electronic image pickup devices are now expanding. Decreased image pickup planes need a finder system of higher magnification. Although it is necessary to shorten the focal length of the whole finder optical system so as to make finder magnification high, this renders it difficult to set up a finder system in a widely available penta prism mode. Another technique known in the art is to use a relay type finder optical system, as typically taught in patent publications 3 and 4. Never until now, however, is there proposed any relay optical system, and any eyepiece optical system that is of good performance, is suitable for use with a small image pickup lane, and can be compactly laid out.
Further, there is still desired an eyepiece optical system or lens that ensures a relatively wide field of view, a long distance (eye relief) from the eyepiece lens the viewer's pupil (eye point), and a compact whole length inclusive of the position of an image being viewed as set by an image-formation lens, and a display position. Such eyepiece optical systems as set forth in patent publications 5 and 6 have so far been available. However, although they have a sufficiently wide angle of view, yet they are of inadequate eye relief.
Still, an eyepiece optical system having a long eye relief is desired in view of camera body construction as well.
Patent Publication 1
JP (A)) 9-329820
Patent Publication 2
JP (A) 2003-91027
Patent Publication 3
JP (A) 4-337705
Patent Publication 4
JP (A) 1-101530
Patent Publication 5
JP (A) 8-43749
Patent Publication 6
JP (A) 9-54258